The Powerlink of Internet Of Things

In the age of data, connectivity is of prime importance. Even the industrial world has set foot into the Industrial Internet of Things. Data can be easily acquired if it is done using standard and open interfaces. This forms the crux of a successful IIOT Implementation.

Industrial Internet of Things: Today and Tomorrow

The office IT network is built on Ethernet and has access to the internet, cloud etc. To access the field information from the board the field level communication also needs to be based on Ethernet. This enables smooth transition of data without the use of gateways. But using standard Ethernet in the field is not advisable as it is prone to the Carrier Sense Multiple Access with collision detection mechanisms (CSMA/CD). In the automation world the machines and processes demand a real time deterministic communication. “Combining the needs of the industry and demands of the machines and processes we come to a conclusion that the automation network should be open source with standard interfaces and having a deterministic system performance” quotes Bhagath Karunakaran, “Ethernet POWERLINK satisfies all these requirements. It is completely open source and truly hardware and software independent. It couples benefits of standard Ethernet interfaces complying with the IEEE 802.3 as in internet of things and the determinism and availability needs of the industrial IOT.”

Ethernet POWERLINK provides determinism down to 100µs. Looking at the software platforms, its implementation can be over Windows, Linux, VXWorks, QNX, and any other operating system or without an operating system. It is also hardware independent with implementation possibilities right from micro-controller, micro-processor, ARM, FPGA, PCI cards, and PCs. The complete source code is available open source, free of cost and is certified and managed by the Ethernet POWERLINK Standardization Group which is a consortium of over 3200 members and users. It equips the user to have a complete choice of topology for his machine and process viz. line, star, tree and ring or a combination of all.

Simple steps to start implementation

There could be different needs of different players who are involved in building the machine, process or IIoT project. If one is an OEM or a system integrator looking to buy off the shelf components then you could talk with companies such as B&R, Cognex, Baumer, ABB etc. for their POWERLINK components. If one is an OEM looking to add custom built embedded components to an off-the-shelf design or a sensor manufacturer such as encoders, temperature sensors, and controllers then one can use openPOWERLINK resources available on sourceforge and build his own hardware or one can choose a module available off-the-shelf and integrate it in his device on that platform.

The openPOWERLINK stack along with the documentation can be found at http://openPOWERLINK.sourceforge.net. It includes the master and slave stack source code, reference designs on multiple silicon and operating system platforms, FPGA IP cores for high performance MAC and for daisy chaining HUBs, and configuration tools.

If you are a start-up or a university student then there is a readily available openPOWERLINK implementation on Raspberry Pi2. It involves a managing node and 2 controlled nodes working on Linux and communicating data on POWERLINK. The complete procedure for installing Linux, building the openPOWERLINK libraries and downloading them in the kits is provided on the website http://www.ethernet-powerlink.org/en/raspberrypi2/. This is the easiest method to bring up a POWERLINK network and to work with all the features offered by the technology.

Ease of working with POWERLINK

Barry Wehmiller International implemented this technology on the critical UV curing controllers needed for the printing industry. Barry Wehmiller International is a global consulting company providing engineering and automation solutions for manufacturing organizations around the world. They have developed controllers for critical UV curing applications for one of their customers in the printing industry. These controllers are equipped with multiple control interface like analogue HMI, web HMI, TCP messaging and Ethernet POWERLINK. “We used openPOWERLINK stack version v2.0.0 and achieved a completely real time deterministic response without any performance issues. The protocol was very easy to implement and took us just 2 days of training from Kalycito to establish POWERLINK communication.” says Srinivasan Subramani ”We conducted 72 hours long test and found a completely error free, deterministic response from POWERLINK. The oscilloscope test results and wireshark traces confirmed the robustness of POWERLINK. Our engineers were impressed with the robustness and reliability of POWERLINK protocol”. The specifications and technical documentation are well drafted and on top of it are available freely online on the EPSG website. The source forge forums provide a perfect arena for availing quality and timely support while implementation.

Barry Wehmiller International used the v2.0.0 stack of openPOWERLINK available on the website ‘openpowerlink.sorceforge.net’. The first step tried out during implementation was to install the openPOWERLINK demo which is also available on the same website on two laptops and establish POWERLINK communication between them. They were unknown to this technology before downloading the stack and working with the demo. When the demo was installed on laptops, they were able to see the exchange of data on POWERLINK. A wireshark trace run on one of the laptop confirmed the data exchange over POWERLINK. Srinivasan says “We were surprised see the demo on two Windows based laptops communicating as a managing node and controlled node in no time and without any prior experience with the technology. This gave our engineers a confidence boost to work with POWERLINK.”

The system consists of a UV controller communicating to the B&R PLC acting as a main printer controller over POWERLINK. This UV controller is also equipped with a web server implementation over the same Ethernet POWERLINK network. Thus the OEM can access the UV controller from anywhere around the world. The UV curing system was able to achieve a a low response time inclusive of the web server implementation and a very high asynchronous bandwidth.

Needs of an IIoT implementation: High availability, high speed and high security

Bhagath was instrumental in specifying redundancy in POWERLINK back in 2005 and POWERLINK since then is equipped with a multi-master, media and ring redundancy. This feature minimizes the downtime, has an extremely fast changeover and is easy to use. “POWERLINK is thus the only industrial Ethernet protocol to provide master source code and specifications free of cost. We have now raised the bar by making redundancy available open source “mentions Bhagath Karunakaran.

POWERLINK thus address the need of availability on the machine and plant level. Security also needs to be addressed as it is also an important issue in the IIoT space. POWERLINK owes much of its unparalleled level of security to the fact that it is open-source software. The stack’s source code and any modifications to it are subject to frequent review by the community. This not only prevents security issues – they are discovered and eliminated long before they can do any harm – but also provides effective protection against hidden backdoor attacks. POWERLINK combines timeslot and polling procedures to achieve isochronous data transfer. How the master node addresses the controlled nodes can be configured by software developers using suitable engineering tools, though this is not transparent to other entities in the network. “The fact that there is no way whatsoever for users to access these network configuration details during system runtime eliminates the need for specific protection against fraudulent manipulations in the system itself” says Ninad Deshpande “High speed regardless of network size, total and complete openness, high tolerance to electrical interference, line and master node redundancy and inherent security that stops attackers in their tracks – POWERLINK fulfills all of these criteria.”

Automation meets the IT

POWERLINK enables the user to gather data from the field in a deterministic method. On a shop floor there could be requirements for the controllers from different machines to exchange data or a central PC working as SCADA would require the data for sending it to the ERP and MES. The machine builders could use OPC UA which is another open source protocol based on standard Ethernet for transferring the data. Being based on standard Ethernet, POWERLINK effectively mergers well with OPC UA and facilitates seamless data transfer from the shop floor to the MES/SAP. With the features such as openness, usage of standard interfaces, compliance with IEEE 802.3, determinism, high availability, and security provided by Ethernet POWERLINK at the field level coupled with its cooperation with OPC UA to transfer data from the field level to the process, ERP, MES layers, has brought IIoT implementation into reality.

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